RHEL5 vsftpd 问题

cat /etc/vsftpd/vsftpd.conf

配置好vsftpd后，客户端登陆：
em@ubuntu:~$ ftp 172.18.30.88
Connected to 172.18.30.88.
220 (vsFTPd 2.0.5)
Name (172.18.30.88:em): ftp
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
200 PORT command successful. Consider using PASV.
425 Failed to establish connection.
ftp> bye
221 Goodbye.

出现红色错误，也不能进行上传。